Plug lock

ABSTRACT

A lock for a conventional electrical plug comprising a frame and bolt which cooperates with the frame to secure the lock to the prongs of the plug, thereby to short circuit the prongs of the plug and to prevent the same from being inserted into a conventional electrical outlet until the lock is removed. In a specific embodiment, the frame and bolt have openings therein which coincide when the frame and bolt are in a locking position such that the shackle of a padlock can be positioned in the openings thereby to prevent the frame and bolt of the lock of the invention from being removed from a plug without removing the padlock from the lock.

I United States Patent [151 3,662,320 Marx 1 May 9, 1972 s41 PLUG LOCK 2,844,805 7/1958 Darrell ..339/37 [72] Inventor: Arthur J. Marx, 1048 Indian Hm Blvd. 3,535,899 10/1970 Gardner et al ..339/37 X van Ohm 4589] Primary Examiner-David H. Brown [22] Filed: Dec. 24, 1970 Assistant ExaminerTerrell P. Lewis 1 pp No 101 262 Attorney-Hood, Gust, Irish, Lundy & Coffey [57] ABSTRACT [22] 3| ..339/37, Nggi A lock for a conventional electrical plug comprising a frame 8230/57 and bolt which cooperates with the frame to secure the lock to I 1 o c 70/58 the prongs of the plug, thereby to short circuit the prongs of the lug and to prevent the same from being inserted into a P conventional electrical outlet until the lock is removed. ln a [56] References Cited specific embodiment, the frame and bolt have openings UNITED STATES PATENTS therein which coincide when the frame and bolt are in a locking position such that the shackle of a padlock can be 3,416,123 12/1968 Husebo ..339/37 positioned in the openings thereby to prevent the frame and 2,733,416 l/l956 Evalt..... ....339/37 bolt of the lock of the invention from being removed from a plug without removing the padlock from the lock. unsta et a 3,345,600 l [[1967 Scherer ..339/37 11 Claims, 9 Drawing Figures P'A'TENTEDHAY 9 I912 SHEET 1 0F 2 ATTORNE PATENTEDHM 9 I972 SHEET 2 0F 2 INVENTOE, ARTHUR J. MARX ATTORNEYS.

PLUG LOCK The present invention relates to a device for preventing conventional electrical plugs of the type having two parallel prongs from being used and more particularly, to a lock which can be secured on a plug in a manner to short circuit the prongs of the plug and to prevent the same from being inserted into a conventional electrical outlet until the lock is removed.

2. Description of the Prior Art Locks for electrical plugs have heretofore been proposed. However, many of these devices have been unduly complicated and inconvenient to use. Many of these devices include several pieces and parts, and some of these devices include conventional lock mechanisms including tumblers and the like. Other devices include only a few parts, but the parts are structurally complicated such that the parts cannot be easily or inexpensively manufactured. It is therefore desirable to provide an improved plug lock which is simple in construction and can be relatively easily and inexpensively manufactured and conveniently used.

SUMMARY OF THE INVENTION It is an object of this invention to provide an improved plug lock.

It is another object of this invention to provide an improved plug lock including only a few pieces, each of which can be relatively easily and inexpensively manufactured by conventional techniques.

It is yet another object of this invention to provide an improved plug lock which can be relatively easily and inexpensively manufactured by conventional techniques from conductive materials, for example, metals, and secured to a plug in a locking position so as to electrically short circuit the prongs of the plug and to prevent the same from being inserted into a conventional electrical outlet thereby rendering the plug inoperative until the plug lock is removed.

A further object of this invention is to provide an improved plug lock comprising two pieces each of which can be inexpensively manufactured and which when secured to a plug in a locking position can be held in that position by a conventional padlock such that it cannot be removed from the plug without mutilating the plug lock or the padlock.

In the broader aspects of this invention, there is provided a lock for an electrical plug of the type having two parallel prongs each of which has an opening therein adjacent to the distal end thereof comprising a frame and a bolt which cooperates with the frame when the bolt is assembled on the frame in a locking position to secure the frame and the bolt to the prongs of the plug, the frame or the bolt having an element which is positioned in the opening of the prong.

BRIEF DESCRIPTION OF THE DRAWINGS The above-mentioned and other features and objects of this invention and the manner of attaining them will become more apparent and the invention itself will be best understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings wherein:

FIG. 1 is a perspective and fragmentary view of a preferred embodiment of the plug lock of this invention secured to a plug showing the plug lock held in its locking position by a conventional padlock;

FIG. 2 is an exploded, perspective view showing the two pieces of the plug lock of this invention illustrated in FIG. 1, disassembled;

FIG. 3 is a top view of the frame of the plug lock illustrated in FIGS. 1 and 2;

FIG. 4 is a fragmentary, broken-away and sectional view of the plug lock of this invention shown in FIGS. I through 3, taken substantially along the section line 4-4 of FIG. 3;

FIG. 5 is an end view of the frame of the plug lock of this invention illustrated in FIGS. 1 through 4, taken substantially along the line 5-5 of FIG. 3;

FIG. 6 is a perspective view of a second preferred embodiment of the plug lock of this invention shown assembled and in a locking position in solid lines and exploded and disassembled in dashed lines;

FIG. 7 is an exploded, perspective view showing the two pieces of a third preferred embodiment of the plug lock of this invention;

FIG. 8 is an exploded, perspective view showing the two pieces of a fourth preferred embodiment of the plug lock of this invention; and

FIG. 9 is a perspective view of a sheet of metal from which the frame of the plug lock illustrated in FIG. 8 is formed.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, and specifically to FIGS. l-5, there is shown a preferred embodiment of the plug lock 10 of the invention. Plug lock 10 comprises a frame 12 and a bolt 14. The frame 12 and bolt 14 are assembled as'shown and cooperate together to function as a plug lock, as will be described hereinafter.

Frame 12 comprises a flat end portion 16 and a formed end portion 18. Portion 16 is provided with an opening 20 centrally located therein and an upset boss or like device 21, the purpose of which shall be mentioned hereinafter. Portion l6 and portion 18 define the opposite ends of frame 12.

Portion 18 has an elongated groove 22 therein extending from portion 16 the entire length of portion 18, groove 22 has opposite open ends 24 and 26. Groove 22 is provided with a bottom 28, upstanding sides 30 and 32 and portions 34 and 36 which are spaced from and overlie bottom 28. As can be seen from the drawings, bottom 28 is a continuation of a surface of portion 16.

Frame 12 also is provided with side portions 38 and 40. Portions 38 and 40, respectively, upstand beyond portions 34 and 36 and are spaced apart a distance greater than sides 30 and 32. Portions 38 and 40 have facing surfaces 42.

Bottom 28 is provided with spaced openings 46 and 48. Opening 46 is adjacent to side wall 30 and portion 38. Similarly, opening 48 is adjacent side wall 32 and portion 40. Secured to both portions 38 and 40 is a protrusion 44. Both protrusions 44 extend from surfaces 42 toward each other; however, protrusions 44 do not extend beyond sides 30 and 32. Protrusion 44 on portion 38 is positioned in opening 46. Protrusion 44 on portion 40 is similarly positioned in opening 48.

Bolt 14 is provided with a flat end portion 50 and a tongue portion 52. Portion 50 is shown to have the same shape and dimensions as portion 16 of frame 12. An opening 54 is provided in portion 50 in a centrally located position, such that when portion 50 is superposed on portion 16 and bolt l4-and frame 12 are assembled as shown in FIG. 1, opening 54 and opening 20 can be coaxially positioned.

Tongue 52 is elongated and extends from portion 50. Tongue 52 and portion 50 are the opposite end portions of bolt 14. Tongue 52 has opposite sides 56 and 58. Sides 56 and 58 are parallel and extend the entire length of tongue 52. An elongated slot 60 is positioned in tongue 52. Slot 60 has opposite sides 62 and 64 which are spaced from and are parallel to sides 56 and 58. Slot 60 is spaced from the distal end of tongue 52 and opening 54.

In operation, bolt 14 can be assembled on frame 12 by inserting tongue 52 in groove 22 and securing the upset boss 21 in slot 60. With the tongue 52in groove 22, tongue 52 is posi tioned between bottom 28 and overlying portions 34 and 36 with tongue sides 56 and 58respectively positioned adjacent to frame sides 30 and 32 such that tongue 52 cannot be removed from slot 22 unless the frame or the tongue is deformed from the shape illustrated. In this locking position, tongue sides 56 and .58 are spaced from portions 38 and 40.

The upset boss 21 and slot 60 allow tongue 52 to slide in and out of the locking position in the direction shown in FIG. 2, but prevent the frame 12 and bolt 14 from becoming disassembled in normal use.

As shown in FIGS. 1 and 4, the prongs 64 and 66 of a conventional electric plug can be positioned in the openings 46 and 48 and the tongue 52 can be slid into groove 22 and positioned between prongs 64 and 66. Protrusions 44 are positioned in the openings 68 of the prongs 64 and 66 and prongs 64 and 66 are positioned between surfaces 42 and tongue sides 56 and 58, as shown in FIG. 4. Openings 68 or recesses which function similarly to openings 68 as far as this invention is concerned are conventional electrical plugs of the type illustrated.

When plug lock of this invention is assembled on a conventional electric plug and positioned in the locking position as described, plug lock 10 cannot be removed from the plug without deforming either bolt 14 or the frame 12. Since the openings and 54 can be coaxial in this position, a shackle 68 of a conventional padlock 70 can be positioned in the openings 20 and 54. In this manner, lock 70 will ensure that plug lock 10 will remain on the plug until it is removed by a person having a key to lock 70.

Referring now to FIG. 6. a second preferred embodiment of the plug lock of this invention is shown. This embodiment 10a comprises a bolt 14a and a frame 12a. A suffix herein will be used to denote like but different parts of two embodiments. Frame 12a has opposite end portions, portion 72 and tongue portion 74. Tongue portion 74 is shown to be an elongated member having parallel sides 76 and 78 and an opening 54a therein. Portion 72 has an opening 80 therein, opening 80 having opposite facing sides 82 and 84. Extending from opposite sides 82 and 84 are protrusions 44a. Protrusions 44a extend into opening 80 from sides 82, 84 toward each other. Portion 72 also includes a strap 86. Strap 86 is spaced from tongue portion 74 by opening 80. 7

Bolt 14a has a tongue portion 52a and a grooved portion 88. Tongue portion 52a and grooved portion 88 are the opposite end portions of bolt 14a. Tongue 52a has opposite parallel and spaced apart sides 56a and 580 which extend the entire length of tongue 52a. Grooved portion 88 includes a groove 22a defined by a bottom 28a, opposite sides a, 32a and overlying portions 34a and 36a. Bottom 28a has an opening 20a therein.

In operation, embodiment 10a functions similarly to embodiment 10 above-described. In this embodiment, prongs 64 and 66 of plug 65 are inserted into opening 80 and the protrusions 44a are inserted into openings 68 of the prongs. The bolt 14a is assembled on portion 74 of the frame as illustrated with tongue portion 74 in groove 22a and tongue portion 52a beneath strap 86. The tongue portion 52a is positioned between prongs 64 and 66, thereby securing the plug lock 10a to plug 65. Openings 20a and 54a, respectively, are provided in portion 74 of frame 12a and portion 88 of bolt 400 such that a shackle 68 of a padlock 70 can be positioned in the openings when the bolt 14a and frame 12a are assembled as abovedescribed.

Referring to FIG. 7, a third preferred embodiment of the plug lock of this invention is shown. This embodiment comprises a frame 12b and 'a bolt 14b.

Frame 12b comprises a flat end portion 16b and a formed end portion 18b. Portion 16b is provided with an opening 20b centrally located therein. Portion 16b and portion 18b define the opposite ends of the frame 12b.

Portion 18b has a groove 22b formed therein. Groove 22b has a bottom 28b, upstanding side 30b and 32b, and portions 34b and 36b which are spaced from and overlie groove bottom 28b.

Frame-12b is provided with spaced openings 46b and 48b. Openings 46b and 48b are spaced form opening 20b by groove 22b. Openings 46b and 48b have facing surfaces 90 and 92. A protrusion 44b is secured to and extends from each of the surfaces 90 and 92. Protrusions 44b are respectively located in openings 46b and 48b and extend toward each other.

18b of frame 12b. Member 94 is spaced from groove 22b by the openings 46b and 48b. Member 94 comprises an end-wall 98 and a portion 100 which is spaced apart and overlies the surface of portion 18b which is in the same plane as groove bottom 28b. Portion 100 has a portion 102 thereon which extends between the surfaces and 92 of the openings 46): and 48b.

Bolt 14b is provided with a flat end portion 50b and a tongue end portion 52b. Portion 50b is shown to have the same shape and dimensions as portion 16b of frame 12b. An opening 54b is provided in portion 50b in a centrally located position such that when bolt 14b is positioned in groove 22b with the distal end of tongue end portion 52b in close proximity to end wall 98 of member 94 and with portion 50b superposed on portion 16b, openings 54b and 20b are coaxial.

Tongue portion 52b is elongated and has opposite sides 56b and 58b. Sides 56b and 58b are parallel and extend the entire length of tongue 52b. Positioned between sides 56b and 58b is an upset boss or like device 21b which cooperates with slot 96 in frame 12b in a manner similar to device 21 and slot 60 of the preferred embodiment illustrated in FIGS. 1 through 4. Boss 21b and slot 96 prevent the frame 12b and bolt 14b from becoming disassembled in normal use.

In operation, embodiment 10b functions similarly to embodiments 10 and 10a above-described. Bolt 14b is assembled in slot 22b and connected to frame 12b by device 2112 and slot 96. The prongs 64 and 66 of a plug 65 are inserted into openings 46b and 48b and the protrusions 44b are inserted into the openings 68 of the prongs. Slot 96 will allow the bolt 14b to be slid into a locking position in which portion 50b is superposed on portion 16b and openings 20b and 54b are coaxial. In this locking position, the distal end of the tongue portion 52b is positioned closely adjacent to end wall 98 of end member 94 and between overlying portion 100 of end member 94 and the facing surface of portion 18b of frame 12b. Further, in this locking position, tongue portion 52b is positioned between the prongs 64 and 66 as in the prior embodiments l0 and 10a hereinabove described.

Referring now to FIGS. 8 and 9, a fourth preferred embodiment 10c of the plug lock of this invention is shown. This embodiment 10c comprises a bolt 14c and a frame 120. Frame 12c is formed from a strip 104 of material such as that shown in FIG. 9. Strip 104 is elongated with opposite sides 106 and 108 and opposite ends 110 and 112. Sides 106 and 108 are spaced apart and parallel. Ends 110 and 112 are also spaced apart and parallel, thereby giving strip 104 an elongated rectangular shape. Intermediate sides 106 and 108 and ends 1 10 and 112 is positioned a rectangular opening 1 14. Opening 114 has opposite sides 116 and 118 which are spaced apart and parallel to strip sides 106 and 108. Opening 114 also has opposite ends 120 and 122 which are similarly spaced apart and parallel to strip ends 110 and 112. Secured to sides 116 and 118 are two protrusions 44c. Protrusions 44c are positioned in opening 114 and extend toward each other.

Strip 104 has two openings 20c therein. Openings 200 are positioned, respectively, between opening 114 and the strip ends 1 10 and 1 12. One of the openings 200 is adjacent to end 1 10; the other opening 200 is adjacent to end 112.

Strip 104 is bent and formed into the shape illustrated in FIG. 8. Strip portions adjacent to the opposite ends 110 and 112 are superposed one over the other in a manner such that ends 110 and 112 are in the same plane and openings 200 are coaxial. Adjacent to ends 110 and 112, strip 104 is formed into a grooved portion 124 having a groove therein in which bolt 14c may be positioned. Sides 106 and 108 from end to end of groove portion 124 are joined together as by crimping or welding, or the like. The portion of strip 104 surrounding opening 114 is folded about lines 126, 128 and 130 into formed portion 132 of frame 12c and the shape shown in FIG.

8. Opening 114 provides an end opening 134 in formed portion 132.

Bolt 140 is provided with opposite sides 56c and 58c which extend the entire length of bolt portion 140. These sides are spaced apart and parallel to each other as in the previously described embodiments 10, a and 10b. Adjacent to one end 136 of bolt Me a stop 138 is provided and an opening 540. Both the thickness of bolt 14c and the distance between sides 56c and 58c are such that bolt 14c can be positioned within the groove of groove portion 124.

In operation, embodiment 10c functions similarly to embodiments 10, 10a and 10b above-described. Prongs 64 and 66 are inserted into the end opening 134 and the protrusions 44c are inserted into the openings 68 of the prongs. Bolt 140 is inserted into the groove portion 124 of the frame 12c and stop 138 is engaged to the frame 12c. In this position, bolt 14c is positioned between the prongs 64 and 66 and the prongs 64 and 66 are positioned, respectively, between opening sides 116 and 118 and bolt sides 56c and 580, thereby securing the plug 65 to plug lock 10c. In this position, openings 200 are coaxial with opening 54c such that a shackle 68 of a padlock 70 can be positioned therein.

As shown and described, each of the embodiments of the invention comprise two pieces made of electrically conductive material. Each of the pieces may be formed of sheet metal and manufactured utilizing only punching and pressing machinery. This allows the plug lock of this invention to be manufactured relatively inexpensively.

Further, it will be noted that once the plug lock of this invention is locked to a conventional plug with a conventional padlock in the manner described hereinabove, the plug lock of this invention cannot be removed therefrom by a person not having a key to the padlock without deforming the pieces of the plug lock or destroying the padlock. So long as the plug lock of the invention is secured to the plug, the plug cannot be used as the plug lock of the invention will short circuit the prongs of the plug and prevent the plug from being inserted into a conventional electrical outlet. It should be noted that the shackle 68 of a single padlock 70 can be positioned within the openings 20, 54 or 200, 54a of more than one plug lock of this invention, if desired.

While there have been described above the principles of this invention in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation to the scope of this invention.

What is claimed is:

l. A lock for an electrical plug of the type having two parallel prongs each of which has an opening therein adjacent to the distal end thereof comprising: a frame having a surface against which a prong of a plug can be positioned, and a bolt which cooperates with said frame when said bolt is assembled on said frame in a locking position to secure said frame and bolt to the prongs of a plug, one of said frame and bolt having an element thereon which is positioned in the opening of a prong positioned adjacent to said surface and the other of said frame and bolt holding said element in said opening when said frame and bolt are assembled on a plug and are in said locking position, at least one of said frame and bolt being an electrical conductor and electrically connecting the prongs of a plug when said bolt and frame are assembled thereon and in said locking position, and means for holding said frame and bolt in a locking position wherein said frame partly surrounds said bolt when said frame and said bolt are in said locking position, said bolt being slidable into and out of said locking position, said element extending in a direction transverse to the direction in which said bolt slides into and out of said locking position.

2. The lock of claim 1 wherein said frame has a slot therein, said slot having a bottom and an upstanding side, said frame having a portion thereof overlying said bottom, said bolt being slidably positioned in said slot between said bottom and frame portion.

3. The lock of claim 2 wherein said bolt when said bolt and frame are in said locking position and assembled on a plug is positioned between the prongs of the plug.

4. The lock of claim 3 wherein said frame bottom has an opening therein in which said adjacent prong is positioned when said frame is positioned on a plug.

5. The lock of claim 4 wherein said surface is the surface of one of said frame sides and said element is secured to said surface, said element extends toward the other of said frame sides.

6. The lock of claim 4 further comprising a second element secured to said other frame side, said elements extending outwardly of said frame sides toward each other so as to be positioned on the openings, respectively, of the prongs of a plug when said frame and bolt are assembled thereon.

7. The lock of claim 4 further comprising means for holding said frame and bolt together in assembled condition.

8. The lock of claim 4 wherein said means for holding said bolt and frame in said locking position are openings in both said bolt and frame which are coaxial when said bolt and frame are in said locking position, whereby the shackle of a padlock can be positioned in said openings.

9. The lock of claim 1 wherein said frame and bolt assembled on a plug and in said locking position are secured to both prongs of said plug.

10. The lock of claim 1 wherein said frame has opposite ends, each opposite end having an opening therein, one of said end openings being the entrance to a slot in which said bolt is positioned when said frame and bolt are assembled, the other end opening is partially bounded by said frame surface against which a prong of a plug on which said frame is assembled is positioned.

11. The lock of claim 10 wherein said bolt is positioned in both of said end openings when said frame and bolt are in said locking position. 

1. A lock for an electrical plug of the type having two parallel prongs each of which has an opening therein adjacent to the distal end thereof comprising: a frame having a surface against which a prong of a plug can be positioned, and a bolt which cooperates with said frame when said bolt is assembled on said frame in a locking position to secure said frame and bolt to the prongs of a plug, one of said frame and bolt having an element thereon which is positioned in the opening of a prong positioned adjacent to said surface and the other of said frame and bolt holding said element in said opening when said frame and bolt are assembled on a plug and are in said locking position, at least one of said frame and bolt being an electrical conductor and electrically connecting the prongs of a plug when said bolt and frame are assembled thereon and in said locking position, and means for holding said frame and bolt in a locking position wherein said frame partly surrounds said bolt when said frame and said bolt are in said locking position, said bolt being slidable into and out of said locking position, said element extending in a direction transverse to the direction in which said bolt slides into and out of said locking position.
 2. The lock of claim 1 wherein said frame has a slot therein, said slot having a bottom and an upstanding side, said frame having a portion thereof overlying said bottom, said bolt being slidably positioned in said slot between said bottom and frame portion.
 3. The lock of claim 2 wherein said bolt when said bolt and frame are in said locking position and assembled on a plug is positioned between the prongs of the plug.
 4. The lock of claim 3 wherein said frame bottom has an opening therein in which said adjacent prong is positioned when said frame is positioned on a plug.
 5. The lock of claim 4 wherein said surface is the surface of one of said frame sides and said element is secured to said surface, said element extends toward the other of said frame sides.
 6. The lock of claim 4 further comprising a second element secured to said other frame side, said elements extending outwardly of said frame sides toward each other so as to be positioned on the openings, respectively, of the prongs of a plug when said frame and bolt are assembled thereon.
 7. The lock of claim 4 further comprising means for holding said frame and bolt together in assembled condition.
 8. The lock of claim 4 wherein said means for holding said bolt and frame in said locking position are openings in both said bolt and frame which are coaxial when said bolt and frame are in said locking position, whereby the shackle of a padlock can be positioned in said openings.
 9. The lock of claim 1 wherein said frame and bolt assembled on a plug and in said locking position are secured to both prongs of said plug.
 10. The lock of claim 1 wherein said frame has opposite ends, each opposite end having an opening therein, one of said end openings being the entrance to a slot in which said bolt is positioned when said frame and bolt are assembled, the otheR end opening is partially bounded by said frame surface against which a prong of a plug on which said frame is assembled is positioned.
 11. The lock of claim 10 wherein said bolt is positioned in both of said end openings when said frame and bolt are in said locking position. 